EP3957909A1 - Four à lit fluidisé asymétrique destiné à la combustion de matières - Google Patents

Four à lit fluidisé asymétrique destiné à la combustion de matières Download PDF

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Publication number
EP3957909A1
EP3957909A1 EP20191986.7A EP20191986A EP3957909A1 EP 3957909 A1 EP3957909 A1 EP 3957909A1 EP 20191986 A EP20191986 A EP 20191986A EP 3957909 A1 EP3957909 A1 EP 3957909A1
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EP
European Patent Office
Prior art keywords
fluidized bed
zone
fluidized
bed
fluidizing
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EP20191986.7A
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German (de)
English (en)
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EP3957909B1 (fr
Inventor
Stefan Hamel
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Steinmueller Engineering GmbH
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Steinmueller Engineering GmbH
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
    • F23C10/00—Fluidised bed combustion apparatus
    • F23C10/18—Details; Accessories
    • F23C10/20—Inlets for fluidisation air, e.g. grids; Bottoms
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
    • F22B31/00—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus
    • F22B31/0007—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus with combustion in a fluidized bed
    • F22B31/0084—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus with combustion in a fluidized bed with recirculation of separated solids or with cooling of the bed particles outside the combustion bed
    • F22B31/0092—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus with combustion in a fluidized bed with recirculation of separated solids or with cooling of the bed particles outside the combustion bed with a fluidized heat exchange bed and a fluidized combustion bed separated by a partition, the bed particles circulating around or through that partition
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
    • F23C10/00—Fluidised bed combustion apparatus
    • F23C10/18—Details; Accessories
    • F23C10/24—Devices for removal of material from the bed
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
    • F23C10/00—Fluidised bed combustion apparatus
    • F23C10/18—Details; Accessories
    • F23C10/24—Devices for removal of material from the bed
    • F23C10/26—Devices for removal of material from the bed combined with devices for partial reintroduction of material into the bed, e.g. after separation of agglomerated parts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
    • F23C6/00—Combustion apparatus characterised by the combination of two or more combustion chambers or combustion zones, e.g. for staged combustion
    • F23C6/04—Combustion apparatus characterised by the combination of two or more combustion chambers or combustion zones, e.g. for staged combustion in series connection
    • F23C6/045—Combustion apparatus characterised by the combination of two or more combustion chambers or combustion zones, e.g. for staged combustion in series connection with staged combustion in a single enclosure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
    • F23C7/00—Combustion apparatus characterised by arrangements for air supply
    • F23C7/002—Combustion apparatus characterised by arrangements for air supply the air being submitted to a rotary or spinning motion
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
    • F23G5/00—Incineration of waste; Incinerator constructions; Details, accessories or control therefor
    • F23G5/30—Incineration of waste; Incinerator constructions; Details, accessories or control therefor having a fluidised bed
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
    • F23C2202/00—Fluegas recirculation
    • F23C2202/30—Premixing fluegas with combustion air
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
    • F23C2900/00—Special features of, or arrangements for combustion apparatus using fluid fuels or solid fuels suspended in air; Combustion processes therefor
    • F23C2900/06041—Staged supply of oxidant
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
    • F23G2202/00—Combustion
    • F23G2202/10—Combustion in two or more stages
    • F23G2202/101—Combustion in two or more stages with controlled oxidant supply
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
    • F23G2203/00—Furnace arrangements
    • F23G2203/50—Fluidised bed furnace
    • F23G2203/502—Fluidised bed furnace with recirculation of bed material inside combustion chamber

Definitions

  • the invention relates to a fluidized-bed furnace and a method for operating the fluidized-bed furnace for the combustion of substances, in particular materials with high calorific values, problematic composition and/or a high proportion of volatile components, comprising a stationary-type fluidized-bed reactor and a free space above the fluidized-bed reactor for post-combustion .
  • Fluidized bed technology has been used successfully for the combustion of coal and sewage sludge for decades.
  • the range of fuels has been steadily expanded with, for example, biomass, biogenic residues, waste, production waste through to alternative fuels and other input materials processed from waste, such as paper sludge, RDF ( Refuse Derived Fuel ), SRF ( Solid Recovered Fuel ).
  • RDF Refuse Derived Fuel
  • SRF Solid Recovered Fuel
  • the fluidized bed itself consists primarily of bed material, consisting of sand and fuel ash, with a small proportion by mass of the fuel also being in the bed.
  • the fluidized bed is fluidized using the so-called primary air, which is introduced as evenly as possible over the reactor cross-section by a gas distributor in order to achieve safe and uniform fluidization.
  • the solids are moved three-dimensionally and thus mixed in the horizontal and vertical directions. This results in an even distribution of fuel and thus temperature within the bed.
  • the uniform temperature distribution and the comparatively low fluidized bed temperature are the main advantages of fluidized bed combustion compared to grate and dust firing.
  • the fluidized bed mass acts as a mobile heat accumulator and compensates for fluctuations in fuel quality with regard to calorific value, pollutant content and water content.
  • EP 0 431 163 A1 refers to a fluidized bed for incineration of various types of waste, characterized by the formation of internal circulation of the bed material.
  • the internal circulation is caused by different fluidization velocities in different zones of the fluidized bed.
  • EP 2 933 557 A1 discloses a fluidized bed furnace composed of a furnace body, a movable bed plate, a first fluidized bed plate, a second fluidized bed plate, a fan and a turbo fan.
  • the floor of the fluidized bed furnace has openings that are only permeable for the fluidizing gas.
  • the bed material is transported to the extraction openings specially designed for this purpose and drawn off there.
  • An internal bed circulation is set up, which ensures that the bed material is transported away.
  • the fluidizing medium is introduced into the fluidized bed via diffuser plates inclined towards the outlet.
  • the fluidizing medium exits at two different exit velocities using two diffuser plates, creating a circulating vortex flow.
  • EP 0 740 109 A2 describes a stationary fluidized bed for the combustion of various materials, such as waste and coal.
  • the design of the fluidized bed furnace described takes particular account of the removal of non-combustible components of the feedstock, such as ash, impurities or agglomerates.
  • EP 3 124 862 B2 describes in figure 1 discloses a fluidized bed furnace having incombustible matter outlet openings located in the bottom of a fluidized bed furnace.
  • the fluidized bed furnace also includes different fluidized bed areas that have different fluidization speeds. Immersion heating surfaces are arranged in the fluidized bed area with a lower fluidization speed.
  • the principle of the stationary or bubble-forming fluidized bed is available as a variant of the process.
  • particular attention must be paid to the fluidized bed temperature in order to prevent agglomerations in the fluidized bed in connection with other difficult fuel properties such as the composition of the ash and its softening behavior under temperature, as well as the presence of accompanying and disruptive substances.
  • a calorific value of around 18 MJ/kg is often given as the upper limit for the fuel for the stationary fluidized bed.
  • the main reason is the setting of the bed temperature, which should typically be around 850°C, depending on the ash softening behavior, but not higher than the usual 900°C. If the fuel properties cannot be changed, other measures must be taken to ensure safe plant operation.
  • the object of the present invention is to expand the range of use of stationary or bubble-forming fluidized bed reactors with regard to the calorific value of the fuels.
  • fuels some of which have high calorific values, whose ash has a complex composition and/or shows variable softening behavior that is strongly dependent on the temperature (tendency to agglomerate), and a non-negligible proportion of accompanying substances, impurities and volatile components feature.
  • the cross-sectional area of the first zone (B1) comprises from 0.55 to 0.75 and more preferably from 0.60 to 0.75 of the total fluidized bed reactor cross-section.
  • the object is achieved by a stationary type fluidized bed furnace by means of an asymmetric operation.
  • Various features control the temperature within the fluidized bed furnace, so that in particular substances with a high calorific value that have a high volatile content can be burned with the apparatus according to the invention.
  • the apparatus according to the invention makes it possible at the same time to ensure the removal of agglomerates and impurities and to ensure the post-combustion of the volatile components entering the free space from the fluidized bed.
  • the structure also realizes a staged combustion of the volatiles within the fluidized bed furnace in order to avoid local temperature peaks in the free space.
  • the present invention relates to a fluidized bed furnace of the stationary type comprising a fluidized bed reactor (A) which is set up to form a fluidized fluidized bed, comprising a first zone for heat recovery (B1) comprising a fluidized fluidized bed area with immersion heating surfaces (E) and a fluidizing gas distributor (C1) with fluidiser elements (6), a second zone for primary combustion (B2) comprising a fluidized fluidized bed area without immersion heating surfaces and a fluidising gas distributor (C2) with fluidiser elements (6'); wherein the fluidization of the fluidized bed area of the second zone (B2) has a higher speed than that of the first zone (B1), so that material circulation (F) within the fluidized bed occurs between the first and second zone.
  • A fluidized bed reactor
  • A fluidized bed reactor
  • A which is set up to form a fluidized fluidized bed, comprising a first zone for heat recovery (B1) comprising a fluidized fluidized bed area with immersion heating surfaces (E) and a fluidizing gas distributor (C1) with fluidiser
  • the cross-sectional area of the first zone (B1) of the fluidized bed comprises from 0.4 to 0.75, preferably from 0.55 to 0.75 and more preferably from 0.60 to 0.75 of the total fluidized bed reactor cross-section.
  • the fluidized bed furnace also has a bed material discharge funnel (D), which connects in the area below the fluidizing gas distributors (C1, C2), and a free space above the fluidized bed reactor (A), in which burnout air nozzles (3) within burnout air levels are arranged.
  • D bed material discharge funnel
  • the fluidized bed reactor is a bubbling fluidized bed reactor.
  • “Fuels” within the meaning of this invention are basically substances that contain a certain proportion of combustible material, which in turn converts the stored energy into usable energy through oxidation, mostly in the form of combustion.
  • combustible materials may include various coals, tailings sludge, oil coal or oil coke, as well as wastes of all kinds and the like.
  • a great advantage of the fluidized bed furnace according to the invention for the combustion of fuels is the thermal utilization or elimination of problematic substances. For example, petroleum coke (a lot of sulphur), chicken manure (low density), landfill gas (low calorific value) and much more can be converted.
  • wastes with a high calorific value that can be used energetically can be used for this purpose, such as animal meal, shredder light fraction, etc.
  • the different fuels can be used both individually (mono-combustion) and in a combination of different fuels.
  • the cross-sectional area of the first zone (B1) comprises from 0.4 to 0.75 of the total fluidized bed reactor cross-section, preferably from 0.55 to 0.75, and more preferably from 0.60 to 0 ,75.
  • the zones of the fluidized bed reactor are subdivided in a way that enables the person skilled in the art to carry out the invention described and bring about the technical effect according to the invention.
  • the entire cross section of the fluidized bed is represented by the horizontal Cross-section at the top of the fluidized bed and is divided into two zones (B1, B2) by an imaginary line.
  • the imaginary line runs in the middle between the fluidizing gas distributor of the first zone (C1) and the fluidizing gas distributor of the second zone (C2), so that the imaginary line is at the same distance from the fluidizing gas nozzles of both fluidizing gas distributors (C1, C2). is.
  • the basic ratio of the area ratio of the first zone of the fluidized bed (B1) to the total cross-sectional area is 40% or higher.
  • the proportion of the first zone (B1) is more than 50% based on the reactor cross section
  • the imaginary line separating the two zones from one another separates, shifted towards the second zone (B2) so that an asymmetric arrangement of the faces (B1, B2) along the axis formed by the imaginary line is obtained.
  • the area percentage of the first zone (B1) is preferably 55% or higher, particularly preferably 60% or higher, of the total reactor cross section.
  • the zones of the fluidized bed have different fluidization rates.
  • a first zone has a fluidization velocity that is less than the fluidization velocity of the second zone.
  • F bed-internal material circulation
  • the entire bed material and thus also the fuel particles distributed throughout the bed material are captured.
  • the formation of agglomerates takes place during fluidized bed operation.
  • the fluidized bed furnace according to the invention is able to at least partially prevent the formation of the agglomerates, alternatively to destroy them, or else to remove them via the discharge funnel.
  • the higher fluidization speed within the second zone causes higher impulses, e.g. between bed material and agglomerates, resulting in more intensive bed material movement and thus promoting the dissolution of agglomerates.
  • the bed material ie the solid that is fluidized to form a fluidized bed in the fluidized bed reactor, is a substance or a mixture of substances that does not itself take part in the combustion.
  • the bed material is most often formed from ash, the solid residue from the combustion of organic matter, and, for example, gravel (sand), with approximately one to three percent by weight of the fuel used being added.
  • the bed material leads to erosion, ie mechanical wear and tear of refractory building materials, eg the immersion heating surfaces arranged within the fluidized bed.
  • erosion is to be rated negatively and leads to high material wear. This effect increases proportionally to the fluidization speed.
  • the slower fluidization is provided in the cooled zone of the fluidized bed (B1) to minimize erosion on the immersion heating surfaces arranged there.
  • fluidization takes place more quickly in order to drive the circulation of the solids and to break up any agglomerates that may have formed.
  • the stationary type fluidized bed furnace according to the invention is operated asymmetrically at least with regard to the fluidizing gas quantity distribution within the fluidized bed material.
  • the specific amount of fluidizing gas supplied in the first zone of the fluidized bed (B1) is correspondingly smaller than the specific amount of fluidizing gas in the second zone of the fluidized bed (B2), the specific amount of fluidizing gas corresponding to the amount of fluidizing gas in kg per m 2 of the fluidized bed area.
  • the fluidized bed furnace is preferably arranged in such a way that the specific amount of fluidizing gas based on the fluidized bed area of the second zone (B2) is at least 150% of the specific amount of fluidizing gas based on the fluidized bed area of the first zone (B1).
  • An even more preferred embodiment comprises a fluidized bed furnace constructed in such a way that the specific amount of fluidizing gas based on the fluidized bed area of the second zone (B2) is at least 200% of the specific amount of fluidizing gas based on the fluidized bed area of the first zone (B1).
  • Absolute values of the specific fluidizing gas quantities are to be selected depending on various parameters such as bed particle size distribution, bed temperature, composition of the fluidizing gas.
  • the zones of the fluidized bed are individually supplied with primary air via fluidizing gas distributors (C1, C2).
  • the primary air corresponds to the fluidizing gas, which consists either of air alone or of a mixture of air and recirculated flue gas.
  • the recirculated flue gas usually corresponds to only part of the gas mixture which is produced during the combustion process of substances in the fluidized bed furnace, is collected and returned to the fluidized bed furnace for the combustion of further substances.
  • the recirculated flue gas can be removed at various points, so that it is uncooled, cooled (e.g.
  • the fluidized bed furnace is constructed such that the fluidizing gas fed via the fluidizing gas distributors to the first zone (B1) and the second zone (B2) of the fluidized bed is independently composed of air and/or recirculated flue gas.
  • the faster fluidized zone (B2) of the fluidized bed is preferably designed without internals. This has the advantage that higher gas velocities, i.e. due to greater fluidization, mean that a higher proportion of solids flows upwards. Since the fluidically connected first zone (B1) of the fluidized bed has a slower fluidization of the bed material compared to the second zone (B2), the bed material is sucked into the faster zone (B2), so that internal material circulation and thus good mixing take place. The cooling of the bed material in the first zone (B1) using immersion heating surfaces (E) also ensures that the temperature in the second zone (B2) is also lowered by the internal material circulation.
  • the proportion of recirculated flue gas in the primary air is advantageously adjusted as required and used to regulate the temperature.
  • the proportion of recirculated flue gas should preferably be selected in such a way that a temperature of 950° C. is not exceeded in the faster zone of the fluidized bed (B2).
  • the primary air is selected so that the proportion of oxygen is present in stages.
  • the total oxygen ⁇ Ges supplied to the fluidized bed furnace is made up of the oxygen ⁇ B that is introduced into both zones of the fluidized bed B1 and B2 and of the oxygen that is introduced into the free space. Unless otherwise noted, the oxygen proportions are in each case based on the stoichiometric oxygen requirement for combustion of the total fuel O min introduced.
  • ⁇ Ges has a value from 1.05 to 1.4 and ⁇ B has a value from 0.35 to 0.9, preferably from 0.4 to 0.8.
  • the remaining amount of required oxygen ⁇ ABL is added.
  • the fluidized bed furnace is arranged in such a way that the oxygen content ⁇ B , which is added directly to the fluidized bed, from the oxygen ⁇ B1 introduced into the fluidized bed region of the first zone (B1), from the oxygen ⁇ B1 introduced into the fluidized bed region of the second zone (B2) oxygen ⁇ B2 introduced and the oxygen introduced into the free space, in each case based on the stoichiometric oxygen demand O min for combustion of the total fuel introduced, with ⁇ B1 being greater than ⁇ B2 .
  • ⁇ B1 is 10% to 30% greater than ⁇ B2 .
  • the operation of the fluidized bed furnace can be asymmetrical with respect to the oxygen conditions within the fluidized bed furnace.
  • the fluidizing elements of a fluidizing gas distributor are arranged within a plane below the fluidized bed, with a distance between the individual fluidizing elements so that all fluidizing gas distributors are permeable to agglomerates, bed material and/or impurities that have formed.
  • the fluidizing gas distributor is designed in such a way that only agglomerates that are no larger than the distance between the fluidizing elements can pass.
  • This advantageous arrangement hereinafter also referred to as an open fluidizing gas distributor or an open nozzle base
  • the fluidizing elements of the fluidizing gas distributor (C1) of the first zone (B1) preferably form a plane that slopes down at an angle of 1° to 75° in the direction of the zone (B2), the plane of the fluidizing elements of the fluidizing gas distributor (C2 ) of the second zone (B2) is preferably aligned horizontally.
  • the fluidizing elements are preferably individual nozzles that are each supplied with a fluidizing gas. It is particularly preferred that the fluidizing elements are nozzles that sit on a nozzle bar that is filled with fluidizing gas for the number supplied by the nozzles located on the beam.
  • the nozzle bar is preferably straight, curved or ring-shaped. It is advantageous that the fluidized bed furnace is constructed in such a way that, starting from the slowly fluidized zone of the fluidized bed (B1), the fluidizing elements are arranged downwards towards the fast fluidized zone of the fluidized bed (B2) (see also figure 6 ). In this way, the internal fluidized bed circulation is additionally supported.
  • a closed nozzle base which is formed from diffuser plates, for example, is often used.
  • a closed nozzle bottom e.g. the sum of the diffuser plates, has no passage between the fluidizing elements, e.g. nozzles, so that in this case the bed material is transported away along the closed nozzle bottom by means of a central or lateral opening.
  • This has the disadvantage that, in particular, fuels that contain higher amounts of impurities, e.g. non-combustible materials or agglomerates, cannot be converted.
  • Advantageous embodiments of the fluidized bed furnace according to the invention also contain at least one side wall of the fluidized bed reactor (A), preferably in the region of the fluidized bed of the first zone (B1), which is arranged widened upwards by an opening angle ⁇ with respect to the vertical.
  • the opening angle ⁇ is 0° or more, preferably 5° or more, more preferably 15° or more.
  • the asymmetrical arrangement of the side walls of the fluidized bed reactor generally favors the flow of solids through the fluidized bed, but in particular the downward-flowing movement of the coarse particles at the edge of the first zone of the fluidized bed.
  • the height of the fluidized bed is preferably chosen so that the immersion heating surfaces (E) in the fluidized bed of the first zone (B1) are either completely surrounded by the bed material or partially protrude into the free space of the fluidized bed furnace.
  • the highest amount of heat can be absorbed.
  • the proportion of the uncovered immersion heating surface increases, the proportion of the absorbed heat quantity also decreases, so that the cooling effect of the immersion heating surfaces on the temperature of the fluidized bed decreases accordingly. In this way, the temperature in the fluidized bed can be regulated depending on the combustion properties of the substances to be burned.
  • At least one substantially vertically arranged guide body (I) is immersed in the fluidized bed between the fluidized bed of the first zone (B1) and the fluidized bed of the second zone (B2), so that there is a distance to the nozzle bottom and to the fluidized bed surface, wherein the geometric base area of the guide body (I) is flat or three-dimensional.
  • the guide body (I) preferably serves as an additional heat transfer surface.
  • the guide body (I) is preferably shaped with tapering inflow sides at the bottom and rounded outflow side at the top. If the fluidized-bed furnace has a guide body (I), this leads to an increase in circulation throughout the fluidized bed.
  • the technical effect of the guide body (I) only comes into its own if the immersion heating surfaces are arranged perpendicularly to the side surface of the guide body, as is shown in figure 8 is shown.
  • the immersion heating surfaces themselves preferably fulfill the function of the guide body (I).
  • the fluidized bed furnace has a discharge hopper for the discharge of bed material, ash and impurities.
  • the opening of the bed material discharge hopper (D) may be located below the first zone (B1), below the second zone (B2) or centered below the fluidized bed reactor (A).
  • the walls of the bed material discharge hopper (D) are preferably designed as additional heat transfer surfaces.
  • the walls of the fluidized bed reactor (A) are configured entirely or partially as heat transfer surfaces, preferably as evaporators.
  • the bed material discharge funnel (D) comprises additional gas supply nozzles.
  • additional gas feed into the discharge funnel (D) also leads to further cooling of the solid to be discharged. This also promotes the ejection of the solids without influencing the amount of heat inside the reactor, because the gas flowing in through the hopper (D) cools the solids to be removed and then rises warmed up in the fluidized bed.
  • the fluidized bed furnace has a free space above the fluidized bed reactor (A), in which combustion air nozzles (3) are arranged within combustion air levels. These burnout air nozzles (3) are preferably aligned within a burnout air plane tangentially to an imaginary tangential circle (G) lying in the free space of the reactor cross section.
  • the free space of the fluidized bed reactor (A) comprises at least a second burnout air level, the burnout air nozzles (3') of which are tangentially aligned to an imaginary tangential circle (H) lying in the free space of the reactor cross section, the tangential circle (G) of the first burnout air level having a different diameter than the Tangential circle (H) of the second burnout air level.
  • the combustion air nozzles (3') of the second combustion air level are arranged at the same level as or above the combustion air nozzles (3) of the first combustion air level.
  • the free space comprising the burnout air levels or the burnout air level forms a so-called burnout zone in the free space of the fluidized bed furnace above the fluidized bed.
  • the post-combustion gas is also referred to as burnout air and can consist of either air, air mixed with recirculated flue gas, or air mixed with other gases such as vapors and exhaust air.
  • the burnout air is flown into the burnout zone with a high impulse and tangentially aligned in order to obtain a twisted flow, i.e. gas flows twisted into one another, and thus a good mixing of the gases in the free space.
  • the number of burnout air levels is selected as required. The requirement results from the content of volatile components in the fuel used. The higher the volatile content and thus also the proportion of the required burnout air above the fluidized bed, the more levels with burnout air should preferably be provided.
  • the design of several burnout air levels has the advantage that the afterburning of the volatile components is staged in such a way that the temperatures within the fluidized bed furnace do not exceed a certain upper limit, which depends on the fuel itself.
  • Safe plant operation with fuels with problematic fuel properties can also be guaranteed by various other measures to reduce the tendency to agglomerate. Aside from the use of lower bed temperatures, appropriate fluidized bed material is appropriate selected for the fuel used, so that the tendency to agglomerate is prevented or at least reduced.
  • a regular or at least partially continuous replacement of the fluidized bed material with fresh material is also conceivable.
  • Additional additives e.g. mineral substances, can be added to the fluidized bed in order to reduce or prevent the formation of liquid or sticky phases within the fluidized bed reactor.
  • An increased fluidization speed can also contribute to preventing or at least slowing down the accumulation of agglomerates, since agglomerates that have already formed can be broken up again by the stronger bed movement and the larger impulses. At the same time, the stronger fluidization can support the equalization of the temperature.
  • the invention also relates to a method for operating the fluidized bed furnace described.
  • the invention relates to a method for incinerating substances in a stationary-type fluidized-bed furnace, the substances being introduced into a fluidized-bed reactor (A) and being combusted, the fluidized-bed reactor (A) forming a fluidized fluidized bed comprising a first zone for Heat recovery (B1) comprising a fluidized bed area with immersion heating surfaces (E) and a fluidizing gas distributor (C1) with fluidizing elements (6), and a second primary combustion zone (B2) comprising a fluidized bed area without immersion heating surfaces and a fluidizing gas distributor (C2) with fluidizing elements (6'), wherein the fluidizing of the fluidized bed area of the second zone (B2) has a higher speed than that of the first zone (B1), so that a fluidized bed-internal material circulation (F) between the first and second zone along the Immersion heating surfaces sets, and wherein the cross-sectional area of the first en zone (B1) from 0.4 to
  • a fluidized bed temperature and a free space temperature are set that differ significantly from one another.
  • the fluidized bed can be operated, for example, at temperatures below 800°C, above 850°C or between 800°C and 950°C.
  • temperatures can be freely selected.
  • the fugitives are mostly burned in the open air.
  • Fluidized bed furnaces are preferably used in the process according to the invention, the cross-sectional area of the first zone (B1) of the fluidized bed being from 0.55 to 0.75 and more preferably from 0.60 to 0.75 of the total fluidized bed reactor cross section.
  • the process preferably has an oxygen content ⁇ B which is added directly via the fluidized bed. This is made up of the oxygen ⁇ B1 introduced into the fluidized bed area of the first zone (B1), the oxygen ⁇ B2 introduced into the fluidized bed area of the second zone (B2) and the oxygen introduced into the free space, each based on the stoichiometric oxygen demand O min for burning all the fuel introduced, where ⁇ B1 is greater than ⁇ B2 . In preferred embodiments of the method, ⁇ B1 is 10% to 30% greater than ⁇ B1 .
  • the fluidizing elements of a fluidizing gas distributor are preferably arranged within a plane below the fluidized bed. A distance between the individual fluidizing elements is advantageous, so that formed agglomerates, bed material and/or impurities are passed through between the individual fluidizing elements of the fluidizing gas distributor.
  • Contaminants, agglomerates and/or the bed material are preferably drawn off continuously via the bed material discharge funnel (D).
  • the method comprises the tangential inflow of a gas for post-combustion onto an imaginary circle (G) lying in the free space of the reactor cross section.
  • the fuel should preferably be fed in in such a way that distribution in or on the fluidized bed is as uniform as possible.
  • the entire volume of the fluidized bed is preferably used for the fuel conversion.
  • the internal circulation is preferably designed to be even and the fuel distributed homogeneously. Different types of fuel are added to the combustion either individually or one after the other (mono-combustion) or simultaneously in combination.
  • the fluidized bed furnace according to the invention and the method for burning substances in this fluidized bed furnace can in principle be used for all combustible substances. Normally, the combustion of fuels with such high calorific values in classic stationary type fluidized bed furnaces leads to problems such as uncontrollable local temperature peaks and increased agglomeration formation.
  • the fluidized bed furnace is advantageously used for fuels with an average calorific value of more than 15 MJ/kg in the state when they are introduced into the fluidized bed.
  • the fluidized bed furnace can be used for the combustion of fuels with a calorific value of more than 20 MJ/kg as they are placed in the fluidized bed.
  • the fluidized bed furnace according to the invention and the method for burning substances in this fluidized bed furnace can also be used advantageously when fuels are used with a content of volatile components of more than 50% by weight, based on the water- and ash-free fuel substance in the state when it is introduced the fluidized bed.
  • the invention is even more advantageous for fuels with a volatile content of more than 70% by weight, based on the water- and ash-free fuel substance in the state when it is introduced into the fluidized bed.
  • figure 1 shows a preferred variant of the fluidized bed reactor (A) according to the invention for the conversion of feedstocks with a high calorific value.
  • Different Quantities of fluidizing gas (6 and 6') consisting of combustion air (1, 1') or a mixture of combustion air and recirculated flue gas (2, 2') are used, so that a fluidized bed area with slow fluidization (B1) and a Forms fluidized bed area with rapid fluidization (B2).
  • immersion heating surfaces (E) are also used to remove reaction heat from the bed and thus adjust the bed temperature to the desired value.
  • the outflow speed of the fluidizing gas (6') is set higher, preferably much higher, than the outflow speed of the fluidizing gas (6) of the slower area (B1).
  • significantly higher impulses are exerted on the particles in this area (B2), so that the cross-mixing between the slow bed (B1) and the fast bed (B2) is intensified.
  • the arrows (F) represent the main circulation in the fluidized bed. While the upward movement of the bed material is forced in the area of fast fluidization (B2), the bed material preferably sinks again in the slowly fluidized part (B1).
  • combustion air is added as so-called burnout air (3) in the free space above the fluidized bed.
  • figure 2 shows the influence on the bed temperature by varying the fluidized bed height.
  • the method of lowering the fluidized bed is also available.
  • the fluidized bed height is lowered, resulting in less immersion heating surface in the bed, where the high heat transfer coefficients prevail, and thus the heat absorption is reduced.
  • figure 1 a completely immersed heating surface, which can thus absorb the maximum possible amount of heat. The basic operation corresponds to the description figure 1 .
  • Figure 3 and 4 show the geometric design of the fluidized bed cross-sectional area. This can be round, square or rectangular. In figure 3 different variants according to the invention of the arrangement of the immersion heating surfaces (E) are shown in a round reactor cross section.
  • the bed material outlet (4) is located geometrically below the fast fluidized bed (B2). This embodiment is to be favored if, for example, coarse impurities are expected in the input material. Due to the increased fluidization speed, it is also possible to ensure that coarse impurities are discharged through the open nozzle floor in the direction of bed material discharge.
  • the discharge i.e. the outflow of the bed material through local loosening due to the gas addition, can be achieved.
  • the bed material to be drawn off is cooled by the addition of gas (7, 7').
  • the additional gas also called hopper gas (7, 7')
  • the amount of hopper gas added can also vary locally in the hopper (4).
  • the decisive factor here is the extent to which cooling is necessary and the extent to which an addition is necessary to ensure mechanical transport along the sloping funnel.
  • the addition of the hopper gas (7') can be dispensed with for transport reasons, since the hopper slope is very steep here, which ensures that the material is transported away and "slips".
  • the funnel gas On the side of the addition (7), however, it is advantageous to add the funnel gas in order to support the material transport in the direction of the outlet (4) through local loosening.
  • the addition of hopper air (7, 7') may still be desirable in order to cool the material before it is discharged.
  • figure 7 shows a modified embodiment of the fluidized bed according to FIG figure 6 . While the simplest form according to the present invention is a vertical configuration of the side walls in the bed area with either a round cross-section, or with a rectangular, or with a square cross-section, it is advantageous if the side walls are configured differently.
  • the structure in shows an advantageous option for an alternative design figure 7 , in which in particular the wall of the fluidized bed reactor (A) associated with the first zone of the fluidized bed area (B1) widens slightly upwards (shown here by the opening angle ⁇ with respect to the vertical). This widening favors the flow of solids through the fluidized bed and in particular the coarse particles flowing downwards in the edge zones, ie on the wall of the fluidized bed reactor.
  • FIG 8 shows an alternative embodiment of the fluidized bed reactor (A) with built-in guide body (I).
  • a guide body (I) can advantageously be used to support the solids circulation that occurs within the fluidized bed. This is inserted vertically between the slow fluidized bed (B1) and the fast fluidized bed (B2) so that it is immersed inside the bed. There is a distance to the nozzle floor at the bottom and to the fluidized bed surface at the top, so that the bed material can follow the preferential circulation (F), but is supported in the direction of circulation by the guide body (I).
  • the guide body (I) can also be designed as a heat transfer surface, like the immersion heating surfaces (E), but can also be designed simply as a body without a heat absorption function.
  • the guide body can, as in figure 8 be schematically indicated fluidically advantageous shaped. For example, with tapered inflow sides at the bottom and rounded outflow side at the solids overflow at the top.
  • exemplary arrangements of the burnout air nozzles are shown in a reactor cross section.
  • the fuels to be used are characterized by a high calorific value with often difficult ash properties at the same time, which tend to agglomerate and which can also contain impurities. These properties, such as those that occur in a wide variety of waste, residues or processed waste fractions, are often accompanied by a high content of volatile components.
  • the design of the combustion air addition in the free space of the fluidized bed furnace according to the invention provides for an injection method above the fluidized bed to produce a sufficiently large amount of mixing.
  • figure 9 shows the exemplary arrangement of the burnout air nozzles in the case of a circular reactor cross section.
  • the outflow direction of a part of the nozzles (3) is aligned tangentially to a larger virtual tangential circle (G) lying centrally in the cross section.
  • Another part of the nozzles (3') is aligned tangentially to a smaller virtual tangential circle (H) lying centrally in the cross section.
  • the same method of adding burnout air can also be used in the case of square or rectangular cross-sections, as in figure 10 shown as an example.
  • the combustion air (3, 3') can consist of air or a mixture of air and recirculated flue gas (recigarette gas).
  • Recigas can be added to the burnout air in a targeted manner, on the one hand to increase the discharge impulses of the nozzles, which improves the mixing in the flue gas flow (5) and/or to lower the temperature in the post-combustion zone due to the presence of Recigas.
  • a further improvement in the post-combustion zone which can be achieved, for example, by improving the mixing and/or by grading the addition of burnout air, thus enlarging the reaction zone, which in turn helps to avoid temperature peaks, can be achieved by increasing the level of the burnout air addition ( 3) and (3') is chosen differently.
  • the means that the injection of the combustion air is carried out in that the injection directed at the "small" tangential circle (H) takes place above or below the injection directed at the "larger" tangential circle (G).

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Fluidized-Bed Combustion And Resonant Combustion (AREA)
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2023218128A1 (fr) * 2022-05-12 2023-11-16 Valmet Technologies Oy Agencement de grille et procédé

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0431163A1 (fr) 1988-08-31 1991-06-12 Ebara Corporation Chaudiere a lit fluidise a circulation composite
EP0722067A2 (fr) * 1995-01-12 1996-07-17 KABUSHIKI KAISHA KOBE SEIKO SHO also known as Kobe Steel Ltd. Dispositif de récupération de chaleur pour lit fluidisé
EP0740109A2 (fr) 1995-04-26 1996-10-30 Ebara Corporation Dispositif de combustion à lit fluidisé
JP2001132925A (ja) * 1999-11-09 2001-05-18 Babcock Hitachi Kk 流動床焼却炉
US20070014704A1 (en) * 2005-07-14 2007-01-18 Hiroshi Hashimoto Fluidized-bed gasification furnace
KR101375873B1 (ko) * 2012-12-18 2014-03-18 한국생산기술연구원 경사진 분산판을 포함하는 유동층 반응기
EP2933557A1 (fr) 2014-04-16 2015-10-21 Ebara Environmental Plant Co., Ltd. Four à lit fluidisé de type tourbillonnaire
EP3124862B1 (fr) 2015-07-28 2019-01-02 Ebara Environmental Plant Co., Ltd. Tube de transfert de chaleur pour chaudière à lit fluidisé
WO2019107421A1 (fr) * 2017-11-29 2019-06-06 川崎重工業株式会社 Four à lit fluidisé

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0431163A1 (fr) 1988-08-31 1991-06-12 Ebara Corporation Chaudiere a lit fluidise a circulation composite
EP0722067A2 (fr) * 1995-01-12 1996-07-17 KABUSHIKI KAISHA KOBE SEIKO SHO also known as Kobe Steel Ltd. Dispositif de récupération de chaleur pour lit fluidisé
EP0740109A2 (fr) 1995-04-26 1996-10-30 Ebara Corporation Dispositif de combustion à lit fluidisé
JP2001132925A (ja) * 1999-11-09 2001-05-18 Babcock Hitachi Kk 流動床焼却炉
US20070014704A1 (en) * 2005-07-14 2007-01-18 Hiroshi Hashimoto Fluidized-bed gasification furnace
KR101375873B1 (ko) * 2012-12-18 2014-03-18 한국생산기술연구원 경사진 분산판을 포함하는 유동층 반응기
EP2933557A1 (fr) 2014-04-16 2015-10-21 Ebara Environmental Plant Co., Ltd. Four à lit fluidisé de type tourbillonnaire
EP3124862B1 (fr) 2015-07-28 2019-01-02 Ebara Environmental Plant Co., Ltd. Tube de transfert de chaleur pour chaudière à lit fluidisé
WO2019107421A1 (fr) * 2017-11-29 2019-06-06 川崎重工業株式会社 Four à lit fluidisé

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2023218128A1 (fr) * 2022-05-12 2023-11-16 Valmet Technologies Oy Agencement de grille et procédé

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